1. Technical Field
This disclosure relates generally to an ignition coil for an internal combustion engine.
2. Background Art
For instance, Japanese Patent First Publication No. 2006-49478 discloses an ignition coil which includes a primary coil, a secondary coil, and a case. The case includes a coil storage casing in which the primary and secondary coils are disposed and a high-voltage tower which extends from the coil storage casing. The high-voltage tower has a resistor which works to minimize noise current generated by a spark plug joined to the ignition coil. The resistor is insert-molded in the high-voltage tower, thereby reducing mechanical stress acting on the high-voltage tower and the resistor as compared with when the resistor is press-fit in the high-voltage tower.
The case is assembled by first placing the resistor in a cavity of a mold made up of a plurality of discrete blocks, injecting molten resin into the mold, and then cooling or solidifying the resin.
The above ignition coil, however, faces the drawback in that the high-voltage tower and the coil storage casing are formed integrally as the case, thus requiring a large size and a complicated shape of the mold to form the case. The case is made by insert-molding the resistor in the high-voltage tower, thus requiring a more complex structure of the mold, which will disturb the productivity of the ignition coil.